I'm missing a piece. I only got 3/4 with the Chef hat, the diskettes shirt and that thief hat. How do I get the last piece?

The last piece you're missing is the moustache. Some hints on how to get it.

Hint 1:Try looking around the track area.Hint 2:You'll notice an item is stuck in one of the speakers (the one at the far left)Hint 3:How might one shake an item loose that's lodged in a speaker?Final Hint:You can get the item by using the microphone to announce your awesomeness. The sound will jar the moustache loose from the speaker. Note that Coach Z will prevent you from using the microphone prior to running the race the first time, so you have to wait until he leaves the field after you lose the first race.